The invention relates to a terminal device, through which ventilation air and recirculating air flows and more particularly to such terminal devices in which supply air is sometimes used to induce at least a part of the recirculating air flow across a heat exchange for heating and/or cooling.
For the cooling of rooms, commonly known systems employ terminal devices in each conditioned space that supply primary air from a central ventilation system. A high velocity may be used to ensure mixing of the air in the conditioned space. The high velocity air may be generated from a mixture of primary and secondary air from the terminal device. If the secondary air also enters the terminal air device via a heat exchanger, or the terminal device includes one, at least part of the heating or cooling load can be satisfied by the heat exchanger load in addition to that provided by the primary ventilation air. A common example of such a system is an active chilled beam.
In active chilled beams, a cooling capacity can be partly satisfied by cold water piped to the chilled beam heat exchanger rather than requiring all of the cooling load to be satisfied by air handlers sized to carry sufficient volumes of cooled air via primary ventilation ductwork. As such, only the ventilation load need be handled by the air handling system. Also, chilled beams are suitable for mounting in ceilings or mounted flush with a suspended ceiling, but since they are standalone components, they can be mounted in many different ways. Latent load must be handled by distributed air, which is fresh, because chilled beams cannot satisfy the latent load of the terminal units themselves because they are not adapted for handling condensate.
Active chilled beams contain a coil in a plenum box hung or suspended from a ceiling. They use ventilation air introduced into the beam plenum through small air jets to magnify the natural induction of air. Active chilled beams have evolved. The term “active chilled beam” became an oxymoron, with active beams being used for cooling and heating. Beams are gaining popularity and are being designed for significantly higher space loads. To match increasing space loads, active beams are specified with higher airflows resulting in systems operating outside of their optimum performance resulting in active beams operating as expensive diffusers.